San Diego  Tourists visit the San Diego Natural History Museum for the big-ticket exhibits featuring dinosaurs, gems or live animals, but for local plant lovers, the museum holds a special appeal.

In January, the museum’s botany department celebrated collecting its 50,000th specimen for the San Diego County Plant Atlas and the collection keeps on growing.

The atlas’ goal is to provide accurate botanical information about the more than 2,000 species of plant that have been documented in San Diego County. Since data collection began in 2002, the museum has used a volunteer force of “parabotanists” who are trained to make collections for the atlas under supervision of scientists.

The museum has trained more than 600 volunteers and there are currently about 125 active ones who scour the county several times a month and return to the museum to process the plant data.

The parabotanists track where each specimen is found, which can lead to new discoveries.

Researchers have found 339 new species and have found other species in curious places as well.

Recently, the volunteers found several desert species located along the coast. At first the museum thought it may have been an error, but after further investigations, discovered it was accurate.

A museum spokeswoman said the change in location can be attributed to various factors, including shifts in wind patterns.

The project will not be completed until the 477 designated areas of the county have been thoroughly explored and had specimens collected from them. Each space is approximately nine square miles in area.

Currently, there are about 50 areas where the museum hasn’t collected a single specimen and nearly 40 where 10 or fewer specimens have been collected. Up to 250 plants have been collected from a single section.

The museum’s botany curator, John Rebman, said he thinks the group is only halfway done with data collection. When the atlas is completed, the museum will use it as a snapshot of the botanic diversity at this point in history.

“It’s a very exciting time,” Rebman said. “As we increase our understanding of plants, our ideas about them are changing. In San Diego, our diversity of plants is just so high we keep learning new things.”